Quantitative Diffusion-Weighted MR Imaging: Is There a Prognostic Role in Noninvasively Predicting the Histopathologic Type of Uveal Melanomas?

Abstract

Histopathologically, uveal melanomas (UMs) can be classified as spindle cell, mixed cell and epithelioid cell type, with the latter having a more severe prognosis. The aim of our study was to assess the correlation between the apparent diffusion coefficient (ADC) and the histologic type of UMs in order to verify the role of diffusion-weighted magnetic resonance imaging (DWI) as a noninvasive prognostic marker. A total of 26 patients with UMs who had undergone MRI and subsequent primary enucleation were retrospectively selected. The ADC of the tumor was compared with the histologic type. The data were compared using both one-way analysis of variance (ANOVA) (assessing the three histologic types separately) and the independent t-test (dichotomizing histologic subtypes as epithelioid versus non-epithelioid). Histologic type was present as follows: the epithelioid cell was n = 4, and the spindle cell was n = 11, the mixed cell type was n = 11. The mean ADC was 1.06 ± 0.24 × 10^-3 mm²/s in the epithelioid cells, 0.98 ± 0.19 × 10^-3 mm²/s in the spindle cells and 0.96 ± 0.26 × 10^-3 mm²/s in the mixed cell type. No significant difference in the mean ADC value of the histopathologic subtypes was found, either when assessing the three histologic types separately (p = 0.76) or after dichotomizing the histologic subtypes as epithelioid and non-epithelioid (p = 0.82). DWI-ADC is not accurate enough to distinguish histologic types of UMs.

Keywords: biopsy; diffusion magnetic resonance imaging (E01.370.350.825.500.150); eye (A01.456.505.420); eye enucleation (E04.540.429); eye neoplasms (C04.588.364); magnetic resonance imaging (E01.370.350.825.500); melanoma (C04.557.465.625.650.510); needle (E04.074.119); prognosis (E01.789); uvea (A09.371.894); uveal neoplasms (C04.588.364.978).

Figure 1

Flow diagram displays the patient selection process.

Figure 2

Epithelioid cell UM. A 65-year-old female patient with a choroidal melanoma of the right eye. Axial (a) T2-weighted turbo spin-echo and (b) fat-suppressed T1-weighted images show a dome-shaped intraocular lesion along the lateral aspect of the globe (white arrows). Along the posterior aspect of the lesion, a serous retinal detachment is detectable on both T2- and T1-weighted images (white arrowheads). On (c) axial DW image (b = 1000 s/mm²) the mass exhibits restricted diffusion with high signal intensity (white arrow), conversely from the retinal detachment that does not show restricted diffusion (white arrowhead). On (d) the axial contrast-enhanced fat-suppressed T1-weighted image, the tumor is enhanced (white arrow); on the other hand, the retinal detachment is not enhanced (white arrowhead). (e) Histological examination: low magnification showing a dome-shaped mass protruding into the posterior segment of the eye and inducing a retinal detachment (H&E, original magnification 25×). (f) High magnification showing the epithelioid cell uveal melanoma composed of nests of polygonal cells with large eosinophilic cytoplasm and rounded nuclei with coarse chromatin (H&E; original magnification 300×).

Figure 3

Spindle cell UM. A 39-year-old male patient with a choroidal melanoma of the left eye. Axial (a) T2-weighted turbo spin-echo and (b) fat-suppressed T1-weighted images display a bulky intraocular mass along the posterior aspect of the globe (white arrows). Axial (c) DW image (b = 1000 s/mm²) and (d) contrast-enhanced fat-suppressed T1-weighted image. The lesion demonstrates restricted diffusion (white arrow in (c)) and moderate enhancement (white arrow in (d)). Note the hemorrhagic retinal detachment on both sides of the mass are more obvious in the T1-weighted images (white arrowheads in (b,d)). (e) Histological examination: low magnification showing a poorly-pigmented tumor protruding into the posterior segment of the eye (H&E, original magnification 25×). (f) Histological detail (higher magnification) revealing a tumor-induced hemorrhagic retinal detachment (black arrowhead) (H&E, original magnification 100×). (g) Higher magnification showing the tumor with spindle cell morphology consisting of spindle-shaped cells with fusiform nuclei arranged in short intersecting fascicles (H&E; original magnification 300×).

Figure 4

Correlation between the ADC value and TP on MRI. Scatterplot (ADC vs. TP) demonstrating that smaller TP tends to have higher ADC values and vice versa (r(24) = −0.87, p < 0.0001). The markers are coded for cell type as follows: ● epithelioid cell type, ● mixed cell type and ● spindle cell type.

Figure 5

Histological features of UMs. (a) Epithelioid cell UM. Large polygonal cells with large eosinophilic cytoplasm and rounded nuclei with coarse chromatin are seen (H&E, original magnification 300×). (b) Spindle cell UM. Fusiform cells with scant elongated cytoplasm, ovoid nuclei and high nuclear-to-cytoplasmic ratio, arranged in short intersecting fascicles, are seen (H&E, original magnification 300×).